A power amplifier may be a fundamental component of a wireless communications device, which may also include transceiver and power source components. In these devices, the power amplifier may be configured to amplify a radio frequency (RF) signal received from the transceiver to allow for communication with other wireless communications devices. The power source may be used to provide a working voltage to the power amplifier.
Two important characteristics of a power amplifier are its efficiency and linearity. Optimizing efficiency may be particularly important in wireless communications devices, where power may be at a premium. Linear operation of the power amplifier may also be important in wireless communications devices because a number of modulation schemes (e.g., IEEE 802.11, Bluetooth, Wi-Fi) may require an amount of linearity in order to avoid transmission errors. Further, nonlinearity may impact the spectral mask, which may be limited by particular standards and regulations of the Federal Communications Commission (FCC).
In power amplifiers, there may be tradeoffs between efficiency and linearity. Efficiency in power amplifiers is generally proportional to input drive level, with maximum efficiency occurring as the power amplifier approaches its maximum output power. Typically, however, power amplifiers cannot achieve linear operation when operating at the high output powers necessary to achieve maximum efficiency. Further, in order to achieve high data rates, some standards (e.g., WiFi, IEEE 802.11a, g, n, ac) use signals with large peak to average ratios (PAR). In order to meet linearity requirements for high PAR signals, the power amplifier may need to operate well under its peak power, which may significantly reduce the efficiency of the device.